Method of reworking a multilayer printed circuit board assembly

ABSTRACT

An improved rework method and rework wiring structure for repairing and reworking multilayer printed circuit boards utilizing ball grid array (BGA) solder pads are described. The repair method includes the steps of locating a solder pad to be rewired, removing the identified pad, installing a repair wire through a via hole in a multilayer printed circuit board, and forming a replacement solder pad on the end of the repair wire and positioning it in place of the removed pad. Once thus installed, the method includes the step of connecting the other end of the repair wire to a corrected circuit interconnection point.

CROSS REFERENCE TO CO-PENDING APPLICATIONS

This application is related to commonly assigned and co-pending U.S.Patent Application. This application is related to commonly assigned andco-pending U.S. Pat. application Ser. No. 09/750,582, filed Dec. 28,2000, and issued as U.S. Pat. No. 6,443,739 on Sep. 3, 2002, andentitled “LGA Compression Contact Repair System”.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an improved method and apparatus for repairingor reworking complex multilayer printed circuit board interconnections;and more particularly to a system of repairing circuit net connectionsusing ball grid array contacts.

2. Description of the Prior Art

It is known to utilize printed circuit boards to make electricalinterconnections between leads of electrical components mounted thereon,including mounted integrated circuits. Printed circuit boardscharacteristically involve one or more discrete layers of insulatingmaterial upon which patterns of electrical conductors are formed inconjunction with a predetermined array of holes. The electricalconductors are referred to as foil. The layers are stacked, bonded, andthe hole patterns formed and plated-through with electrical conductivematerials. Characteristically, plated-through holes are uniform indiameter, and are often referred to as “barrels”. Selectiveinterconnections result in selected wiring networks, or nets, beingformed with various ones of the electrical conductors on differentlayers being interconnected through plated-through holes. Thiseffectively provides a three-dimensional wiring system. At the mountingsurfaces, it is known to provide additional electrically conductivematerial in electrical contact with the plated-through holes for thepurposes of providing an expanded pad area for making interconnectionwith the component contacts, terminals, leads, or mounting contacts.

It has been the usual practice to have the diameter of theplated-through holes uniform throughout the thickness of the multilayerprinted circuit board. With the advent of continued reduction in size ofthe electronic components, the spacing of the component connections hasbeen decreasing, and the density of the associated array of holes hasbeen ever-increasing. As the density of integrated circuit componentsincrease the array of interconnection points to a printed circuit boardmultiplies for the same integrated circuit die size. At the same time,the complexity of the interconnections that are to be made by themultilayer printed circuit boards has increased. This increase in thenumber of interconnections results in the requirement of providing moreconductive routing paths on the various layers, where these routingpaths must be constructed in ever-decreasing dimensions. The loss ofrouting area resulting from the reduction in pin spacing in the gridarray of plated-through holes has lead to the requirement of addingadditional layers to the multilayer printed circuit board assemblies,with the attendant increase in cost of manufacture.

It is known to utilize so-called surface mount components, whererelatively short component leads are affixed to surface pads on themultilayer printed circuit boards. Characteristically, they are affixedthrough a solder process. The surface mount has the problem of locationof all of the terminals of a component over the associatedinterconnection pads during the soldering process. Any misalignment ormisplacement can result in missing or marginal solder interconnections.

A form of surface mount includes the process of mounting packagedintegrated circuits (IC) to printed circuit board assemblies having anarray of pads on the printed circuit board interconnected to a matchingarray of IC contacts through a soldering process that uses solder balls.This interconnected technology is generally referred to as a ball gridarray (BGA).

It is also well-known in the design of the electrical interconnectionsto be made on the printed circuit board assembly, that design problemscan result in wiring network layouts that must be altered or reworked toform correct wiring network interconnections. Further, it is known thatin the fabrication of multilayer printed circuit boards it can occur,for various manufacturing reasons, that one or more layers may haveelectrical conductors improperly electrically shorted to aplated-through hole. Unless such re-routing or shorted condition can berepaired, the entire assembly has to be scrapped. Various types ofrework and repair techniques have been developed, but such known repairand rework techniques are complex; and if not accomplished with skilland precision, can result in further damage to the printed circuit boardand failure to remedy the problem. As the array of printed circuit boardinterconnections become larger there is an increase in the number ofplated-through holes of smaller diameter, and more layers, are utilized,it becomes more and more necessary to have an effective and efficientway to rework incorrect or defect wiring nets to save the boards.

The development of integrated circuits (ICs), including applicationspecific integrated circuits (ASICs), requires on-circuitinterconnection of cells and requires off-circuit interconnections toconnect circuits on different ICs or to connect to connectors or othercomponents, power, ground, and the like. When design errors,manufacturing errors, or design changes occur relative tointerconnection of IC pins, the entire supporting printed circuit boardmust be scrapped unless a repair system is provided.

For those systems where ICs or ASICs were interconnected through metalpins soldered into plated-through holes in the printed circuit boards orto pads on the surface of the printed circuit boards it was possible tosolder the repair wire directly to the pin or surface pad. Thoseresoldering processes usually required the pin to be disconnected fromthe wiring net within the printed circuit board to be accomplished bydrilling out the via hole in the printed circuit board to disconnect theinternal wires. It has been determined, however, that structures thatutilize BGA surface contact solder connection to interconnect the ICs orthe ASICs to the printed circuit board that such a drilling out andresoldering process cannot be accomplished within the tolerances of thestructure. Further, the drilling out process requires very closetolerance and often results in destruction of the solder pad.

Accordingly, it is desirable to have a repair system and method thatovercomes the limitations for repair incident in the prior art.

OBJECTS

It is the primary objective of this invention to provide a method andapparatus to efficiently repair and rework multilayer printed circuitboards.

It is a further primary objective of this invention to provide animproved printed circuit board assembly having an improved structure foruse in affixing electrical components that may be reworked as necessaryto correct design and manufacturing deficiencies.

Yet another objective of the invention is to provide an improved printedcircuit board assembly having a structure for affixing electricalcomponents that is suitable for use with BGA interconnections.

Another objective of the invention is to provide an improved multilayerprinted circuit board assembly having an array of plated-through holesto interconnect selected layers, and a rework structure that can beutilized to rework circuit interconnections with selected ones of theplated-through holes.

A further objective of the invention is to provide an improvedmultilayer printed circuit board assembly for use with an enhancedcapability of rework or repair to allow repair of defects in manufactureand rework of erroneous interconnections of electrical wiring networkswith improved rework structures.

Still a further objective of the invention is to provide an improvedrepair and rework pad structure for use with a multilayer printedcircuit board assembly for effectively and reliably allowing the repairand rework of the assembly to accommodate solder interconnections withintegrated circuits.

Yet another objective of the invention is to provide an improvedreworked pad structure that matches the shape of a removed pad, has aninsulating material deposited on a portion thereof, and a conductiveportion that interacts with a BGA solder pad.

A further objective of the invention is to provide an improved reworkapparatus and method to efficiently and economically rework multilayeredprinted circuit boards to avoid the necessity to scrap defective ordamaged boards.

Other more detailed objectives will become apparent from a considerationof the Drawings and the Detailed Description of the PreferredEmbodiment.

SUMMARY OF THE INVENTION

To overcome the problems in the prior art and improved repair and reworkmethod have been developed wherein the repair and rework method isapplied to rework a circuit connection on a multilayer printed circuitboard that mounts one or more integrated circuits and have apredetermined array of BGA solder pads to interconnect with eachintegrated circuit, wherein the array of pads are electrically connectedto respectively associated via lands on plated-through hole barrels on afirst surface of a printed circuit board, where each of the barrelsextends through the printed circuit board to a second surface. Thebarrels are formed as plated-through holes and interconnect topredetermined wiring nets within the printed circuit board. The repairmethod involves disassembling the integrated circuit from the ball gridarray of solder pads to which the integrated circuit is electricallyconnected, to thereby expose the array of solder pads. A particular padis identified to be repaired, and the identified pad is removed alongwith its associated via pad and interconnecting foil. A repair wire isselected and placed in the associated barrel of the plated-through holefrom which the identified solder pad has been removed, with theinsertion being such that a first end is extended past the first surfaceof the printed circuit board and is available for forming. Onceinstalled, the exposed end of the repair wire is formed into a shape toapproximate that of the removed solder pad. The formed pad is positionedand bonded to the first surface of the printed circuit board. The secondend of the repair wire is routed and connected to the appropriatecorrected circuit connection to complete the rework and repair. Theentire assembly is then reassembled with the removed integrated circuitbrought into electrical interconnection with the array of solder pads,including the newly formed pad formed on the repair wire.

For certain repair functions it, is desirable to provide a selectivecoating on the newly formed solder pad on the end of the repair wire. Byway of example, it may be necessary to coat the replacement repaircontact pad with gold to match the performance of the other pads in theball grid array and to treat the repair pad with solder so that it willproperly make soldered connection when subjected to the solder ballsoldering process.

An improved repaired assembly has been provided and includes amultilayer printed circuit board having first and second surfaces; anarray of BGA solder pads arranged on said first surface to electricallyinterconnect associated contacts on at least one integrated circuitmounted on the multilayer printed circuit board; a plurality ofelectrical wiring nets in the multilayer printed circuit board; aplurality of plated-through holes extending through the printed circuitboard between the first and second surfaces, with selected ones of theplurality of plated-through through holes in a electrical contact withassociated ones of the plurality of wiring nets, and each of theplurality of plated-holes electrically connected to an associateddifferent one of the array of the BGA solder pads; a repair wire havinga first end portion formed in the shape of a solder pad and positionedon the first surface of the printed circuit board to replace a removedone of the array of solder pads, and the repair wire having a boardtransition portion extending through the one of the plated-throughthrough holes that is associated with the removed one of the pads, andthe repair wire having a second end portion extending beyond the secondsurface and making circuit connection to a selected circuitinterconnection point to repair the function of the circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of an integrated circuit package thatutilizes a ball grid array (BGA) system of solder contacts tointerconnect the integrated circuit to an array of solder pads on aprinted circuit board;

FIG. 2 is a partial cross-section view of a portion of the printedcircuit board with a BGA solder interconnection to a plated-through holeand to a repair structure.

FIG. 3 is a cutaway view at 3—3 in FIG. 1 of a portion of a multilayerprinted circuit board having an array of BGA pads and illustrating therepair structure of this invention;

FIG. 4A is a pictorial view of a tool that can form the replacement padshape on a repair wire;

FIG. 4B is a pictorial view of an alternative tool that can form thereplacement pad shape on a repair wire;

FIG. 5 illustrates a repair wire with a shaped replacement pad;

FIG. 6 illustrates a pad-shaping portion of the tool shown in FIG. 4B;

FIG. 7 illustrates the face view of one of the pad shaping elementsdescribed in FIG. 6; and

FIG. 8 is a process flow diagram illustrating the repair and reworkprocess.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is an exploded view of an integrated circuit package thatutilizes a ball grid array (BGA) system of solder contacts tointerconnect the integrated circuit to an array of solder pads on aprinted circuit board. In this configuration of a packaged integratedcircuit 20 is shown separated from printed circuit board 22. Theunderside 24 of the packaged integrated circuit 20 has an array ofcontacts 26 that cooperates with the array of contacts 28 on the uppersurface 30 of printed circuit board 22. The carrier 32 ischaracteristically ceramic and has the array of contacts 26 to be bondedto the integrated circuit contacts (not shown) this array of contacts 26cooperate with an array of solder balls 34, which in turn cooperate withthe array of contacts 28 when the packaged integrated circuit ispositioned in the direction of arrow 36. Printed circuit board 22, shownbroken away, has at least one array of interconnection pads, one of sucharrays being shown within dashed block 28. This array of solder pads 28is adapted to mate with the array of solder balls 34 and the array ofcontacts 26 on the underside 24 of packaged IC 20. Printed circuit board22 has a number of layers supporting a number of interconnecting foils(not shown) for purposes of making interconnection to other componentsor integrated circuits (not shown). An array of the plated-through holes(not shown) in printed circuit board 22 are provided.

When positioned, contact 26 a will be in contact with solder ball 34 a,which in turn will be in contact with solder pad 28 a. All othercontacts 26 will be positioned over associated solder balls 34 and willbe in contact with associated ones of solder pads 28. When thuspositioned, the soldering process is accomplished.

Interconnection between integrated circuits on this type of assembly ischaracteristically through the various printed circuit board foil paths(not shown) that are part of the multilayer printed circuit board 22.When a design is laid out interconnecting specific contacts betweendifferent integrated circuits in a larger assembly or in makingconnection to connectors, it can be determined that wiring errors haveoccurred. When such a condition is encountered, if the wiringinterconnection between integrated circuits or other components cannotbe corrected, the entire printed circuit board assembly 22 must bediscarded. It is toward remedying this condition that the presentinvention is directed.

FIG. 2 is a partial cross-section view at 2—2 of a portion of theprinted circuit board with a BGA solder interconnection to aplated-through hole and to a repair structure. This view shows carrier32 with pads 26 in contact at their up ends 26U to integrated circuit38. Printed circuit board assembly (PCBA) 22 has plated-through hole 40with an upper via land 42U and lower via land 42L. Solder pad 28-1 issoldered 44-1 to its associated contact end 26. Plated-through hole 46has a lower via land 48L but has had its upper via land removed. Repair49 extends through the barrel of plated-through hole 46 and has itsreplaced solder pad end 49P soldered 44-2 to its associated contact 26.

FIG. 3 is a cutaway view at 3—3 in FIG. 1 of a portion of a multilayerprinted circuit board having an array of BGA pads and illustrating therepair structure of this invention. Printed circuit board 22 iscomprised of a number of insulating layers 50 upon which interconnectingfoil is deposited in a predetermined pattern to make interconnectionwith various ones of the plated-through holes. Plated-through holes arecomprised of conductive barrels such as barrels 52, 54, 56, 58, and 60.In addition, each plated-through hole has an upper associated via land62 that is electrically connected to a solder pad 64. Further, each ofthe plated-through holes has an open barrel 66 that extends verticallythrough the thickness of the printed circuit board 22.

In a characteristic array utilizing a BGA solder system to interconnectto mounted integrated circuits, the array of solder pads andplated-through holes can require 1,657 or more connections on onemillimeter centers, or less and can require a thickness 68 of a contactpad to be flat within a tolerance of 0.002 inch.

Interconnection between various ones of the plated-through holes areillustrated by connectors 70, 72, and 74 being connected to barrel 42;conductors 72 and 74 being connected to plated-through barrel 54;conductor 76 being connected between barrels 58 and 60; and conductor 78being connected to plated-through barrel 60. These interconnections areof course by way of illustration only and are merely shown to indicatethat the electrical interconnections to the plated-through-hole barrelswill not be interrupted or changed as a result of the repair process ofthe invention.

A repaired pad is shown utilizing a twisted pair 80 that has one wire 82connected at the lower via pad 84 of barrel 56. The signal wire 86 ispassed upward through the opening 66 of barrel 58. The exposed end isshaped to form a solder pad 88 that is positioned to replace the removedpad 64 from the position to be corrected. Once positioned and adhered tothe surface of printed circuit board 22, the twisted pair 80 can berouted to make the circuit connection correction required.

FIG. 4A is a pictorial view of a tool that can be utilized to form thereplacement pad shape on a repair wire. This tool 90A has a pair of jawmembers 92A and 92B, each having flat compression surfaces of apredetermined depth D that can be utilized to establish the length ofthe portion of the repair wire that is to be reshaped in the form of areplacement solder pad. Handle portions 94A and 96A are shown brokenaway, and are utilized to apply sufficient pressure to jaw members 92Aand 9A to flatten the end of a repair wire to the desired thickness.

FIG. 4B is a pictorial view of an alternative tool that can form thereplacement pad shape on a repair wire. Tool 90B has a pair of opposedjaw members 92B and 94B activated by associated handles 96B and 98B,which are rotatably coupled together by pin 100. Member 94B has aflattened portion 102 in which a wire receiving groove 104 is incommunication with a shaping cavity 106. A mating structure is shown inmember 92B in dashed line. In operation, the stripped tip of wire 86 ispositioned and inserted in the direction of arrow 108 into the receivingaperture 104. When the tip of wire 86 is fully positioned into theshaping portion 106, the tool 90B is closed with sufficient force toflatten the tip of wire 86 into the conforming shape 106.

FIG. 5 illustrates a repair wire with a shaped replacement pad. Once thetip of wire 86 has been formed into shaped portion 88 through the use ofa tool 90A or 90B, it has a shape that approximates the solder padportion 64.

FIG. 6 illustrates a pad-shaping portion of the tool shown in FIG. 4B.This broken away view illustrates opposed jaw members 92B and 94B in aclosed position around the end 88 of wire 86 and illustrates thethinning of the thickness T of portion 88 to a dimension approximating0.002 inch.

FIG. 7 illustrates the face view of one of the pad shaping elementsdescribed in FIG. 6. In this view the face of member 94B is illustratedhaving the wire receiving portion 104 and the shaping cavity 106. Cavity106 approximates the shape of element 88 shown in FIG. 5. It is ofcourse understood that once wire 86 is passed through the appropriateplated-through through barrel opening 66 and in 88 is suitably formed,the replacement solder pad 88 must be bent at right angles to the tip ofwire 86 in order to be put into conformance with the upper surface ofprinted circuit bard 22.

FIG. 8 is a process flow diagram illustrating the repair and reworkprocess.

Once it has been determined that an error condition exists that requireswiring net correction, it is necessary to identify the IC or ASICinvolved, and for the appropriate component, remove the selectedpackaged IC 20. This is necessary to expose the BGA solder pads 28 onthe multilayer printed circuit board (PCBA) 22, as indicated by methodstep 120. Once exposed, the particular pad that is identified to berewired is located and a marker wire inserted in the barrel, asindicated by the method step 122 to locate the pad to be repaired. Oncea pad is identified, the method step of protecting adjacent pads 124 isaccomplished by taping over or other suitable protective measures. Toinitiate the repair, it is necessary to remove the via land, the BGAsolder pad and the interconnecting foil, as indicated by step 126. A vialand is alternatively referenced as a via pad. With reference to FIG. 3,one method of removing the via pad 62 is to utilize a drill bit having adiameter of about 0.020 inch to drill into the via pad thereby removingit. This drilling must be controlled as to the depth of drill to avoidimpacting or disconnecting any of the foil interconnections on theinternal planes of printed circuit board 22. Once via pad 62 is removed,the associated solder pad and any remaining interconnecting conductivematerial is removed by heating it with a heating iron to temperaturethat softens the bonding material and allows it to be raised and removedby a blade. A replacement repair wire can be of the twisted pair 80described with regard to FIG. 3, or can be a single wire as described inFIG. 2, utilized to make circuit interconnections. In the preferredembodiment for the type of printed circuit board 22 described, thetwisted pair wire can be selected as a 34 gauge wire pair. The singlewire can be a 34 gauge magnet wire, it being understood that the twistedpair wire and alternatively the magnet wire have electrical insulationon their respective surfaces at least on the portion positioned withinthe plated-through hole. Once a repair wire is selected, it is necessaryto remove the marker wire and to thread the repair wire through the viahole as indicated by step 128. A sufficient length of wire is threadedthrough the via hole such that it protrudes on both sides of printedcircuit board 22. With either the twisted pair or magnet wire selection,it is necessary to have sufficient wire on the underside of the printedcircuit board to route to the appropriate connection points. The amountof wire extending above the surface of printed circuit board 22 need beonly enough to be gripped by the pad forming tool (see FIG. 4A and FIG.4B). It is then necessary to form a new solder pad on the exposed end ofthe repair wire 130 by physically deforming the end of the repair wireto form the replacement pad. Once formed, the replacement pad is bent atright angles to the barrel of the plated-through hole and is availablefor attachment.

If the printed circuit board to be repaired is for development purposes,the formed solder pad can be the material of the replacement wire. Inthose situations where it is desired that the repaired printed circuitboard have characteristics similar to the array of pads not repaired, itmay be necessary to coat the replacement contact pad with an appropriatematerial. Accordingly, it is necessary to determine whether a specialcoating material is required, as indicated by step 132, and if it isrequired, to add the special coating material per method step 134 to thereplacement solder pad. By way of example, if the solder pads in thearray are all gold plated, it may be desirable to use gold plated wireor to gold coat the replacement pad to enhance solderability. It is alsodesirable to treat the replacement solder pad for the BGA solderingprocess. When the replacement pad 88 is formed and ready for attachment,it is essentially at right angles to the associated barrel comprisingthe plated-through hole. The formed pad 88 is positioned and bonded tothe surface of printed circuit board 22 as indicated by method step 136.Bonding in a preferred embodiment is accomplished by carefully applyinga selected adhesive, which by way of example can be Loctite Takpakadhesive system. Other adhesives may be available or preferred by thoseskilled in the art.

Once the replacement solder pad has been formed and adhered to theprinted circuit board, it is necessary per method step 138 to route andconnect the repair wire the proper connection point. Depending uponwhether a twisted pair magnet wire replacement is utilized, this routingand connection process will differ. When a twisted pair is utilized, asillustrated in FIG. 3, the non-signal wire 82 is characteristicallyelectrically connected to a ground via pad. This interconnection isaccomplished my exposing the tip of ground wire 82 and soldering it tovia pad 84. The twisted pair is then routed to the selected connectionlocations and electrically interconnected as needed. In the event themagnet wire is utilized for making interconnection to another locationwithin the same array of solder pads or is made to a solder contactconnection on a different array, sufficient magnet wire must have beenprovided to allow routing and to allow the extension of the other endthrough another selected plated-through hole barrel for formation ofreplacement solder pad at the other end of the wire. Thatinterconnection would require a similar repeat of steps 122 through 136.

Once the repair wire or wires have been put in place, it is necessaryper method step 140 to determine whether or not a special insulator willbe required. A special insulator may be required to prevent the reworkwires from being pinched. The insulator material is positioned over theunderside of the printed circuit board 22 with the repair wire or wiresvisible. A pattern is formed of the path of the repair wire or wires,and that pattern is cut in the special insulator. The paths thus cutallow the repair wire or wires to be disposed in the cut out area whileallowing the insulator material to lie flush with the underside of theprinted circuit board, all without pinching or deforming the repair wireor wires.

From the foregoing it can be seen at the various objectives and purposesof the invention have been achieved. The use of the replaced solder padsand the associated correction wires results in an improved rework methodand an improved reworked multilayer printed circuit board structure. Therework process and apparatus is extremely cost-effective in that thereworked solder pads and wire interconnections can save time in therepair of development units and can save expensive board structures frombeing scrapped.

The invention has been described in its presently contemplated bestmode, and it is clear that it is susceptible to various modifications,modes of operation and embodiments, all within ability and skill ofthose skilled in the art without the exercise of further inventiveactivity. Accordingly, what is intended to be protected by LettersPatent is set forth in the appended claims.

What is claimed is:
 1. A method of reworking a multilayer printed circuit board having a predetermined array of solder pads electrically connected to respectively associated via lands on plated-through barrels on a first surface of the printed circuit board, each of the barrels extending through the printed circuit board to a second surface and interconnecting to predetermined wiring nets within the printed circuit board and each of the barrels further having an opening, said method comprising the steps of: a. identifying one of the solder pads requiring a changed electrical connection; b. removing the identified solder pad from the first surface without interrupting the wiring net associated therewith; c. selecting a repair wire; d. inserting a first end of the selected repair wire in the barrel opening associated with the identified and removed solder pad until a predetermined portion of the first end is exposed beyond the first surface; e. after insertion of the selected repair wire, shaping the end of the predetermined portion in a shaped end substantially in the shape and thickness of the identified and removed solder pad; f. positioning the shaped end on the first surface in a position to replace the removed identified solder pad; and g. affixing the positioned shaped end to the first surface.
 2. The method of claim 1, wherein said selecting step c includes the further method step of: h. selecting a single wire having a sufficient length to make electrical connection to a predetermined electrical circuit.
 3. The method of claim 1, wherein said selecting step c further includes the method steps of: h. selecting a twisted pair wire having a sufficient length to make electrical connection to a predetermined electrical circuit, including a signal wire and a ground wire; and i. connecting the ground wire to a predetermined ground terminal on the printed circuit board.
 4. The method as in claim 1, and further including the step of: h. coating the shaped end of the repair wire with a predetermined material.
 5. The method as in claim 4, and further including the step of: i. selecting gold as said predetermined material.
 6. The method as in claim 1, on further including step of: h. treating the shaped end for a solder process.
 7. The method as in claim 1, wherein the removing step b includes the methods steps of: h. drilling the via land to a predetermined depth to remove the via land without damage to any wiring net in the printed circuit board; i. heating the identified solder pad sufficiently to soften the interconnection to the first surface of the printed circuit board; and j. lifting the selected solder pad off the first surface.
 8. The method as in claim 1, wherein the shaping step e includes the steps of: h. subjecting the predetermined portion to pressure in a tool until the desired shape and thickness of the shaped end is achieved; and i. bending the shaped end relative to the portion of the repair wire that is positioned in the barrel opening to allow the shaped end to lie flat on the first surface of the printed circuit board.
 9. The method as in claim 8, wherein the affixing step g includes the method step of: j. applying a predetermined adhesive between the shaped end and the first surface of the printed circuit board.
 10. The method of claim 1, wherein said selecting step c includes the further step of h. selecting a single strand wire comprised of magnet wire.
 11. The method of claim 1, wherein said selecting step c further includes the step of h. selecting a single strand wire having electrical insulation material covering all but said predetermined portion formed as said shaped end in accordance with step e.
 12. A method of reworking a circuit connection on a multilayer printed circuit board that mounts one or more integrated circuits and having a predetermined ball grid array of solder pads to interconnect each integrated circuit and electrically connected to respectively associated via lands on plated-through hole barrels on a first surface of the printed circuit board, each of the barrels having an opening and extending through the printed circuit board to a second surface and interconnecting to predetermined wiring nets within the printed circuit board, said method comprising the steps of: a. removing a selected integrated circuit and exposing the array of solder pads requiring circuit alteration; b. identifying and locating a solder pad to be repaired; c. protecting the solder pads adjacent to the located solder pad that could be damaged during the repair process; d. removing the identified solder pad and the via land and interconnecting foil associated with the identified solder pad without interrupting the wiring net associated therewith; e. selecting a repair wire and threading the selected repair wire through the barrel opening associated with the identified solder pad; f. after threading the selected repair wire, forming a replacement solder pad substantially in the shape and thickness of the identified and removed solder pad on the exposed end of the repair wire; g. determining whether or not special coating material for the newly formed solder pad is required, and if required adding the special coating material; h. forming and bonding the newly formed solder pad to the first surface of the printed circuit board; and i. routing and connecting the repair wire to the corrected circuit connection.
 13. The method of claim 12 wherein said selecting step e, includes the further step of j. selecting a single strand wire comprised of magnet wire.
 14. The method of claim 12 wherein said selecting step e, includes the further step of j. selecting a single strand wire having electrical insulation material covering all but that portion formed as a replacement solder pad in accordance with step f. 